1. Field of the Invention
Fuel injection apparatus for an internal combustion piston engine varies the engine output torque by controlling the average fraction of the combustion chamber cycles which receive fuel injection.
2. Prior Art
Gasoline engines generally require some means of controlling their torque output, since the maximum available torque is not always wanted. Conventional gasoline engines have a throttle valve in the air inlet duct which serves as the primary control of engine output torque. The air intake pressure is then sensed and used in adjusting the fuel intake, so that the fuel-air ratio is reasonably close to its optimum value for engine efficiency and low atmospheric pollution. Exact timing of the spark ignition, for good engine efficiency and low atmospheric pollution, is also made to depend on the air intake pressure.
In some multicylinder engines, equal distribution of fuel to the different cylinders is effected by providing a separate fuel injector valve for each cylinder. Fuel is injected during each air intake stroke of each cylinder, the amount of fuel being commonly adjusted automatically in dependence on air intake pressure and other factors. Automatic fuel injection apparatus for this purpose are disclosed, for example, in U.S. Pat. Nos. 3,612,008; 3,612,009; 3,612,010; 3,945,350; 3,983,849 and 3,612,013. The last of these patents discloses a deceleration override circuit which responds to strong throttling of the engine. At engine speeds above idle speeds, the override circuit disables or inhibits the regular fuel injection circuit in order to save fuel and reduce atmospheric pollution.
New gasoline engine design is made difficult by heavy throttling of the air intake, since it affects the amount of fuel needed, vaporization and mixing of the fuel, firing or misfiring, flame propagation, heat transport to the wall, deposition of carbon, detonation, exhaust gas pressure, exhaust gas recirculation, piston blowby, crankcase ventilation, and atmospheric pollution. In developing a new engine, so much experimentation and compromise must be carried out that development of a satisfactory engine may take years.
In my copending U.S. Pat. application no. 735,392, filed 10-26-76, a method of torque control is disclosed which eliminates the need to heavily throttle the air intake. In the preferred embodiment, the average torque output of a single cylinder engine is reduced by inhibiting fuel injection in a fraction of the cylinder cycles. The fraction of fuel rations skipped is varied manually through the intervention of an electronic fuel injection inhibitor. In another embodiment, the fraction of skipped fuel rations is controlled automatically in dependence on engine speed and external load.
Any multicylinder engine with fuel injection needs some means of distributing potential fuel injection pulses to the proper cylinder, so that fuel will be introduced into each cylinder in the proper part of its cycle. An additional requirement for my inhibited engine is a means for distributing the inhibition of injections fairly evenly over the different cylinders.
The injection inhibitor apparatus for a multicylinder engine may simply consist of duplicates of my single cylinder injection inhibitor apparatus, but in such an aggregation the inhibition can be distributed unevenly among the cylinders.
Methods of engine torque control which eliminate the need to heavily throttle the air intake are disclosed in U.S. Pat. Nos. 3,756,205 and 4,040,395. These methods reduce engine output torque by inhibiting the ration of fuel in a fraction of the combustion chamber cycles. Such engines tend to pollute the atmosphere, however, because cylinders that are partially inhibited cannot be used to completely reburn the blowby gases which leak past the pistons into the crankcase.